The present invention relates to current collecting equipment and a method of current collecting for a railway vehicle, such as a high speed railway vehicle.
Aerodynamic noise which is produced by a high speed railway vehicle rapidly increases with increasing speed of the vehicle proportional to approximately the eighth power of its velocity. On the other hand, the concern about preservation of the environment has been growing and will be an important factor in the future. Therefore, it is required for a vehicle running at a high speed (for example, over 270 km/hr) to carry low noise current collecting equipment.
A low noise current collecting equipment is proposed in an article entitled "Speeding up SHINKANSEN" (Nikkei mechanical, published on May 4, 1992, pages 22 to 40). The following is described in this report (especially on page 27).
It is desirable for lowering noise that a member having a contact strip as a current collecting member has a streamlined shape. Taking the combination of the streamline-shaped member and strut supporting the member into consideration, a lifting force takes place. The lift causes the contact strip to become detached from the trolley wire or contacts to the trolley wire with exceeding force to cut the trolley wire. With the provision of two kinds of current collecting equipment depending on the direction of running of the vehicle, switching from the one kind to the other kind is performed at a turn back station. The current collecting equipment is T-shaped and is formed with large sized members in order to decrease any produced frequency vibration.
Further, taking these facts described above into consideration, a view of a T-shaped current collecting equipment is illustrated in FIG. 5 in the paper. This current collecting equipment comprises a member supporting a contact strip with a fine motion spring, a cylinder for raising and lowering the member through a restoring spring, and an insulator supporting the cylinder.
On the other hand, the conventional pantograph type current collecting equipment comprises a pantograph having a contact strip, a pneumatic cylinder for raising and lowering the pantograph, four insulators to support and insulate a support base mounting the pantograph and the pneumatic cylinder, and a conducting cable installed on the roof of the vehicle. The compressed air supply to the pneumatic cylinder is performed with an installed pipe penetrating through the insulator.
Further, other constructions of current collecting equipment for high speed railway vehicles in order to lower noise are also described in Japanese Patent Application Laid-Open No. 5-49103(1993) and Japanese Patent Application Laid-Open No. 5-49104(1993).
The current collecting equipment for high speed railway vehicles, the T-shaped current collecting equipment proposed in the above paper and the current collecting equipment for high speed railway vehicles proposed in the above Japanese Laid-Open Patent Application Applications, are designed to resolve the problems which accompany high speed running. However, since the functions of the pantograph, (1) the function of contacting and following a trolley wire and (2) the function of conducting current to direct collected electric power to the vehicle, are attempted to be provided with only one construction, as in the conventional pantograph, it is difficult to satisfy the seemingly conflicting requirements concerning responsive following of the trolley wire and lowering of noise caused by increasing the vehicle speed.
For example, the conventional T-shaped current collecting equipment has the following disadvantages. First, the cylinder for raising and lowering the contact is positioned on the contact strip side near to the supporting insulator. Therefore, said cylinder for raising and lowering has to be provided as a pneumatic cylinder. Although it is desirable for a high speed vehicle, from the point of view of responsive control, to employ an oil-hydraulic cylinder, the oil-hydraulic cylinder cannot be employed in the equipment.
Further, the raising and lowering cylinder has a control system to maintain the contact pressure against the trolley wire constant and requires means for detecting the contact pressure, such as a load cell, to be used as a control input. The position to set the contact pressure detecting means is on the contact strip side near the raising and lowering cylinder. Since the position is in a portion of the high voltage region, the countermeasure for insulation of the detecting means is required.
Furthermore, although the current collecting equipment is designed for collecting current, the above-mentioned paper does not disclose its current conducting system at all.
With regard to the cylinder that is used to raise or lower the current collecting equipment when it is switched at a turn back station, since the current collecting equipment not being used forms a projection, there is a limit to the lowering of noise produced by the equipment.
It is thought that the current collecting equipment described in the above-mentioned Japanese Laid-Open Patent Applications also have the same problem.